1、前言

通过实现RequestInterceptor接口实现拦截方式，仅能获取接口参数，无法获取接口返回值，因此采用实现Decoder接口方式对接口的入参及返回值进行记录。

2、代码实现

import com.alibaba.fastjson.JSON;
import feign.FeignException;
import feign.Request;
import feign.Response;
import feign.codec.DecodeException;
import feign.codec.Decoder;
import io.micrometer.core.instrument.util.IOUtils;
import lombok.extern.slf4j.Slf4j;

import java.io.IOException;
import java.lang.reflect.Type;
import java.nio.charset.StandardCharsets;
import java.util.Objects;

@Slf4j
public class FeignLogDecoder implements Decoder {
    final Decoder delegate;

    public FeignLogDecoder(Decoder delegate) {
        Objects.requireNonNull(delegate, "Decoder must not be null. ");
        this.delegate = delegate;
    }

    @Override
    public Object decode(Response response, Type type) throws IOException {
        String resultStr = IOUtils.toString(response.body().asInputStream(), StandardCharsets.UTF_8);
        byte[] body = response.request().body();
        String url = response.request().url();
        log.info("{}：参数->{}",url,new String(body,StandardCharsets.UTF_8));
        log.info("{}：返回->{}",url,resultStr);
        // 回写body,因为response的流数据只能读一次，这里回写后重新生成response
        return delegate.decode(response.toBuilder().body(resultStr, StandardCharsets.UTF_8).build(), type);
    }
}

import feign.codec.Decoder;
import feign.optionals.OptionalDecoder;
import org.springframework.beans.factory.ObjectFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.http.HttpMessageConverters;
import org.springframework.cloud.openfeign.support.ResponseEntityDecoder;
import org.springframework.cloud.openfeign.support.SpringDecoder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class FeignConfiguration {

    @Autowired
    ObjectFactory<HttpMessageConverters> messageConverters;

    @Bean
    public Decoder feignDecoder() {
        return new FeignLogDecoder(new OptionalDecoder(new ResponseEntityDecoder(new SpringDecoder(this.messageConverters))));
    }
}

3、实现效果